重复值求和

方法一：sql = "select sum(a.数量) from (select distinct 条码号,数量 from [myTable]) a"
方法二：
 Dim dic As New Dictionary(Of String, Integer) '声明字典
        Dim son As KeyValuePair(Of String, Integer)
        Dim k As Integer = 0
        Dim dt As New DataTable '数据表

        For Each drow As DataRow In dt.Rows
            If Not dic.ContainsKey(drow("条码号")) Then
                dic(drow("条码号")) = drow("数量")
            End If
        Next
        For Each son In dic
            k += son.Value
        Next
        MsgBox(k.ToString)